147. Insertion Sort List

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最新推荐文章于 2024-11-10 21:15:35 发布

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本文深入探讨了链表插入排序算法的实现细节，通过具体的示例解释了算法的工作原理，包括逐步移除输入元素并将其正确插入到已排序列表中的过程。提供了两种不同的Java实现方法，帮助读者理解如何在链表数据结构上应用插入排序。

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147. Insertion Sort List

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Sort a linked list using insertion sort.

A graphical example of insertion sort. The partial sorted list (black) initially contains only the first element in the list.
With each iteration one element (red) is removed from the input data and inserted in-place into the sorted list

Algorithm of Insertion Sort:

Insertion sort iterates, consuming one input element each repetition, and growing a sorted output list.
At each iteration, insertion sort removes one element from the input data, finds the location it belongs within the sorted list, and inserts it there.
It repeats until no input elements remain.

Example 1:

Input: 4->2->1->3
Output: 1->2->3->4

Example 2:

Input: -1->5->3->4->0
Output: -1->0->3->4->5

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode insertionSortList(ListNode head) {
        if (null == head) {
            return head;
        }
        
        ListNode dummyHead = new ListNode(0);
        
        while (head != null) {
            ListNode tNode = head;
            head = head.next;
            
            ListNode nHead = dummyHead;
            while (nHead.next != null && tNode.val > nHead.next.val) {
                nHead = nHead.next;
            }
            
            tNode.next = nHead.next;
            nHead.next = tNode;
        }
        
        return dummyHead.next;
    }
}

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode insertionSortList(ListNode head) {
        if (null == head) {
            return head;
        }
        
        insertionSortList(head.next);
        ListNode ptr1= head, ptr2 = ptr1.next;
        while (ptr2 != null && ptr1.val > ptr2.val) {
            int t = ptr1.val;
            ptr1.val = ptr2.val;
            ptr2.val = t;
            
            ptr1 = ptr1.next;
            ptr2 = ptr2.next;
        }
        
        return head;
    }
}